The project will evaluate the potential benefit of the use of bone replacement graft as an adjunct to surgical therapy of peri-implantitis. The project will be conducted as a two-armed randomized controlled clinical trial of 5-year duration in 7 clinical centers. 140 systemically healthy patients diagnosed with peri-implantitis will randomly assigned to be treated with or without bone replacement graft. Outcome measures include assessments of inflammation, probing depth, recession, radiological parameters and PROMs.